1. Field of the Invention
The present invention relates to a camera having a varifocal lens and, more specifically, to a camera having a varifocal lens in which ratio of an object to a photographing frame can be set.
2. Description of the Related Art
A camera system of particular interest to the present invention is disclosed in, for example Japanese Patent Laying Open No. 63-220118. According to this article, the camera system comprises an apparatus for setting ratio of an object to the photographing frame. The focal length is calculated from the photographing distance and the ratio of the object, and the zoom lens is driven so as to realize the calculated focal length. However, the structure of this camera system is complicated, since it employs a zoom lens.
Therefore, one object of the present invention is to simplify a structure of a camera system in which the ratio of the object to the photographing frame is automatically set.
Another object of the present invention is to ensure focus adjustment in a camera system having a varifocal lens and a focusing lens each driven by a motor.
A further object of the present invention is to change methods for driving respective lenses in correspondence with the capacitance of the driving source for driving the lenses, in a camera system having a varifocal lens and focusing lens.
The above described objects of the present invention can be attained by a camera system comprising a distance measuring apparatus for measuring an object distance, a focal length calculating apparatus for calculating the focal length of the varifocal lens based on the object distance, and a correcting amount calculating apparatus for calculating an amount of driving the focusing lens for correction based on the focal length so as to enable focus detection of the focusing lens during zooming in a range from the infinite photographing position to the closest photographing position.
Since the camera system comprises the above described components, when a prescribed photographing frame is determined, the focal length of the varifocal lens can be calculated based on the object distance at that time, and the focusing lens is moved to a prescribed in-focus position so that the image is in the in-focus state.
Therefore, a varifocal lens is employed in a camera system, in which the ratio of the object to the photographing frame can be set. Consequently, the structure of a camera in which the ratio of the object to the photographing frame can be set is made simple.
In accordance with another aspect of the present invention, the camera system of the present invention comprises a varifocal lens driving apparatus having a zooming motor for driving the varifocal lens, a focusing lens driving apparatus having a focusing motor for driving the focusing lens, a power supply for supplying power to the zooming motor and the focusing motor, a power supply capacity detecting apparatus for detecting the capacitance of the power supply, and a lens driving controlling apparatus for controlling the motors so that the both motors are driven in accordance with the capacitance of the power supply.
Since the camera system comprises the above described components, the varifocal lens and the focusing lens for correcting defocus of the varifocal lens are driven in correspondence with the capacitance of the power supply at the time of photographing.
Therefore, when the capacitance of the power supply is sufficient, both lenses are surely driven, and when the power supply capacity is not sufficient, the lenses are not driven.
Consequently, the focus adjustment can be surely carried out in a camera system having a varifocal lens and a focusing lens.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.